In the prior art chemical solutions such as sulfuric acid are purified by passage under pressure through porous ceramic filters. The apparatus used in the prior art includes gaskets, line seals, or other mechanical pressure seals having joints communicating with the flow path. Inevitably finely divided particulate matter which is often organic in nature works its way around the gaskets or through the mechanical joints being driven by the pressure of the flow used in the filtering step. Thus, these fine particles find their way into the filtered sulfuric acid. These organic particles which have by-passed the filter then become oxidized by the sulfuric acid becoming carbonaceous and they show as black specks and particles in the filtered solution. This by-passing of particulate matter past the filter media has been a continuing problem in the production of purified sulfuric acid and other solutions.